A semiconductor read only memory (ROM) is a type of solid state memory that permanently stores data in that data is generally not lost when power is disconnected from the memory. The semiconductor ROM comprises one or more ROM cell arrays. A ROM cell array comprises one or more ROM cells that are set to either an “on” or “off” state by programming the semiconductor ROM. ROM cells are capable of storing a binary bit of data based upon an accumulation of charge, such as electrons or holes, for example, representing either a logic state of “0” or “1” depending on whether a path of a bit line to ground (VSS) of the ROM cell is electrically connected or isolated. A single-end sensing circuit, such as an inverter, or a differential sensing circuit is used to detect a data state of a ROM cell. For example, a relatively lower voltage state, resulting from little to no accumulation of charge, represents a logic value of “0”, while a relatively higher voltage state, resulting from a greater accumulation of charge, represents a logical value of “1” or vice versa.
To achieve an increase in memory density of semiconductor ROMs, the size of ROM cell arrays has decreased. For example, decreasing OD-to-OD spacing between oxide diffusion (OD) regions that define active source/drain regions for transistors of ROM cells allows for additional ROM cells to be formed within the semiconductor ROM to increase memory density. Unfortunately, decreasing OD-to-OD spacing leads to cell current degradation, commonly referred to as OD space effect. Cell current degradation adversely impacts ROM performance characteristics such as speed and VCCmin performance, where VCCmin corresponds to a minimum voltage at which the ROM operates reliably, for example.